1. Field of the Invention
This invention relates in general to the construction of fluid handling devices and in particular to a new and useful device for throttling fluids which flow through a flexible conduit, and which includes a plate member having a groove thereon in which the conduit is positioned and a cover plate which has a projection thereon of a depth to engage in the groove and means for moving the cover plate and base plate relatively in order to press or release the tube and thus regulate the flow cross section therethrough.
2. Description of the Prior Art
In throttling devices, the pressure reduction is generally obtained through narrow gaps. At the same time, it is usual to reduce the pressure along very short distances, whereby high shearing stresses are produced. To fluids sensitive to shear, for example, blood, milk, and albuminous solutions, high shear stresses leading to shearing within the structural constitution are not beneficial. They reduce the quality.
A flow regulator for adjusting desired flow rates of fluids conveyed through lines is known, in which a flexible tube is surrounded by a controllable throttling device which acts on the circumference of the tube and by which the cross-section of passage is varied. The throttling device comprises a fixed abutment and a lever arm mounted for pivoting about its central portion. Upon pivoting one end of the lever arm, the other end presses the tube against the abutment. By the deformation of the tube the cross section of the passage is varied. The movement of the lever arm is controlled by a step motor through a cam plate. In this flow regulator, the variation of the cross-section is limited to a short length of the tube, so that the pressure is reduced over a short distance. This causes high shearing forces in the fluid to be controlled. Therefore, this flow regulator is not suitable for fluids sensitive to shear (German Offenlegunsschrift No. 21 05 106).
Further known is a micro control device for liquids flowing through flexible conduits, in which the rate of flow is controlled by squeezing the conduit walls in one direction, from opposite sides. The wall of the conduit is squeezed by a lever by which the flexible conduit is pressed through an aperture provided in the wall of the device. The lever may be actuated manually or automatically. The flexible conduit is not only squeezed in its cross section, but also deformed along its longitudinal axis. In this micro control device, the pressure is reduced along a short way. That is why the device is not suitable for liquids sensitive to shear. In addition, it is not advantageous that the material of the conduit is subjected to high stresses (German Offenlegunsschrift No. 23 53 624).